Loading...
Please wait, while we are loading the content...
Similar Documents
Direct numerical simulations of high-speed turbulent boundary layers over riblets
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Choudhari, Meelan, M. Duan, Lian |
| Copyright Year | 2014 |
| Description | Direct numerical simulations (DNS) of spatially developing turbulent boundary layers over riblets with a broad range of riblet spacings are conducted to investigate the effects of riblets on skin friction at high speeds. Zero-pressure gradient boundary layers under two flow conditions (Mach 2:5 with T(sub w)/T(sub r) = 1 and Mach 7:2 with T(sub w)/T(sub r) = 0:5) are considered. The DNS results show that the drag-reduction curve (delta C(sub f)/C(sub f) vs l(sup +)(sub g )) at both supersonic speeds follows the trend of low-speed data and consists of a `viscous' regime for small riblet size, a `breakdown' regime with optimal drag reduction, and a `drag-increasing' regime for larger riblet sizes. At l l(sup +)(sub g) approx. 10 (corresponding to s+ approx 20 for the current triangular riblets), drag reduction of approximately 7% is achieved at both Mach numbers, and con rms the observations of the few existing experiments under supersonic conditions. The Mach- number dependence of the drag-reduction curve occurs for riblet sizes that are larger than the optimal size, with smaller slopes of (delta C(sub f)/C(sub f) for larger freestream Mach numbers. The Reynolds analogy holds with 2(C(sub h)=C(sub f) approximately equal to that of at plates for both drag-reducing and drag-increasing configurations. |
| File Size | 708064 |
| Page Count | 13 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_20140011906 |
| Archival Resource Key | ark:/13960/t49p82394 |
| Language | English |
| Publisher Date | 2014-01-13 |
| Access Restriction | Open |
| Subject Keyword | Aerodynamics Aircraft Design, Testing And Performance Riblets Aerodynamic Configurations Direct Numerical Simulation Drag Reduction Skin Friction Reynolds Number High Speed Turbulent Boundary Layer Free Flow Boundary Layers Mach Number Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
